Control systems for rotatable devices rely upon position feedback for operational control and diagnostics. Rotational angle of the rotatable device can be measured using a rotational angle sensing system. Measurement of a true rotational angle of a rotating shaft is useful when the shaft is connected to an electric machine, e.g., a permanent-magnet synchronous electric motor.
Signal output from a rotational angle sensing system is subject to error due to factors including manufacturing variations and tolerances, including initial alignment of the sensing system during installation. Manufacturers attempt to correct errors using adjustments during assembly and post-assembly calibrations that are embedded into control systems. Manufacturers also utilize such techniques as tight machine tolerances, precision assembly methods and multiple position sensing devices to provide more accurate measures of rotational angle.
Resolver assemblies and other rotational sensing systems can provide precise measurement of the rotational angle. Known resolver devices can be used to measure rotational angle of a shaft, providing a high-resolution signal corresponding to the true rotational angle of the shaft and direction of shaft rotation. The devices are operative over a wide range of ambient temperatures, in the range of −40° C. to +125° C., thus enabling application on a broad range of systems. Applications using resolver assemblies have precise requirements for angular position and speed measurement. It is known that manufacturing variations can affect signal output of the resolver, thus affecting operation of control systems which utilize the signal output from the resolver for control and diagnostics. The accuracy of the rotational angle measurement is directly affected by the installation and mechanical alignment of the resolver.